e1RM Calculator

What is e1RM?

Your estimated 1-rep max (e1RM) is the maximum weight you could theoretically lift for a single repetition, calculated from a submaximal set. Rather than testing your true 1RM (which is fatiguing and risky), you perform a comfortable working set and use a mathematical formula to extrapolate your max.

For example: if you bench press 120 kg for 5 reps at RPE 8, your e1RM is approximately 150 kg. This becomes your planning baseline for all percentage-based and RPE-based programming.

Why Use an e1RM Calculator?

• Safer than max testing — no need to attempt a true 1RM every week
• Tracks progress — rising e1RM across similar sets shows real strength gains
• Programs weights — use your e1RM to calculate exact training loads for any rep/RPE target
• Works for any lift — squat, bench press, deadlift, overhead press and more

e1RM Formulas Compared

Formula	Equation	Best For
Epley	Weight × (1 + Reps / 30)	Most popular; works for 1–10 reps
Brzycki	Weight × 36 / (37 − Reps)	More accurate for lower reps (1–6)
Mayhew	Weight / (0.522 + 0.419 × e^(−0.055 × Reps))	Good for higher rep ranges
RPE-Based (Tuchscherer)	Weight / RPE% from Tuchscherer table	Most accurate when RPE is known

Our calculator uses all four formulas and shows you each result. When you provide an RPE, the Tuchscherer (RPE-based) result is highlighted as the most accurate estimate.

How Accurate is e1RM?

Research shows e1RM formulas are typically accurate within ±5% for sets of 1–6 reps. Accuracy decreases for higher rep sets (8+ reps) and for less experienced lifters who may underestimate their RIR. For the most reliable estimate, use a weight you can lift for 3–6 reps and record your RPE honestly.

e1RM vs True 1RM: Which Should I Use?

For day-to-day programming, use your e1RM — it fluctuates with recovery and gives you a real-time picture of your current strength. Test your true 1RM only at competition or at the end of a training block (every 8–16 weeks), then re-calibrate your e1RM baseline.